0,75 = 75/100 = 3/4 (сократили на 25)
0,5 = 5/10 = 1/2 (сократили на 5)
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(1 1/12 + 3,75) - (-х) = 4,5
1 1/12 + 3 3/4 + х = 4 1/2
1 1/12 + 3 9/12 + х = 4 1/2
4 10/12 + х = 4 1/2
х = 4 1/2 - 4 10/12
х = 4 3/6 - 4 5/6
х = - (4 5/6 - 4 3/6)
х = - 2/6
х = - 1/3
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Проверка: (1 1/12 + 3 3/4) - 1/3 = 4 10/12 - 1/3 = 4 5/6 - 2/6 = 4 3/6 = 4 1/2